Welcome aboard.
There's plenty of info on chokes and mag tube extensions in the 930 sub-forum. If you don't find the answers you're looking for, feel free to post up any questions. There are a lot of knowledgeable folks here that will be happy to help.
We've got a great group of folks here on Mossberg Owners and the atmosphere is very laid back. The only thing we like better than discussing each other's guns is lookin at 'em, so we can't wait to see some pics of your 930. Take a look around and feel free to post up pics of any other firearms you own in the various sub-forums. You'll find that we're into a lot more than just Mossberg around here. Jump in on the conversation anywhere and let us know if you have any questions.
Enjoy the site!
- L.E.S.